On the causes of evolutionary transition:transversion bias

Arlin Stoltzfus; Ryan W. Norris

For purposes of evaluation, we can break down either the mutational hypothesis or the selective hypothesis into (1) a claim that there is an underlying bias (mutational or selective) favoring transitions, and (2) a claim that this bias accounts for the observed evolutionary bias. For the mutational hypothesis, the existence of an underlying bias is indicated in direct studies of mutation (e.g., Schaaper and Dunn 1991; Lynch 2010; Schrider, et al. 2013; Zhu, et al. 2014) , and by many indirect estimates based on the . CC-BY 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/027722 doi: bioRxiv preprint asumption of neutral sequence divergence (Petrov and Hartl 1999; Rosenberg, et al. 2003; Zhao, et al. 2004; Jiang and Zhao 2006; Morton, et al. 2006 ), though Keller, et al. (2007 report a lack of bias in grasshoppers. The bias typically is 2-fold to 4-fold over null expectations. In theory, a bias in mutation of magnitude B can cause a B-fold effect on the rate of evolution (Yampolsky and Stoltzfus 2001; McCandlish and Stoltzfus 2014) . That is, the observed magnitude of mutation bias appears to be sufficient, in principle, to account for the observed evolutionary bias.